In many physical activities, such as golf, baseball, tennis, and the like, correct execution of the activity requires precise movement of at least one movable member, such as the head of the golfer, the arms of the batter, and the tennis racquet of the tennis player. For example, a golfer who lifts his head too early while swinging a golf club will often hit a golf ball incorrectly. Typically, however, the subsequent flight of the golf ball does not provide enough feedback to the golfer as to the correctness of his head position during his swing of the golf club. Consequently, the golfer does not learn from his mistakes as quickly as if he were given immediate feedback as to the cause of the errant shot, namely, his lifting his head too early.
While the particular physical activity of golf is a convenient example for the purposes of describing the present invention and the drawbacks of the prior art, it is to be clearly understood that discussion of the sport of golf does not limit the scope of the present invention to training devices for golf exclusively. The prior art for training devices of the type herein described is primarily concerned with the game of golf.
U.S. Pat. No. 5,005,835 to Huffman on Apr. 9, 1991, teaches a fairly rudimentary golf swing head movement monitoring apparatus. Such a device is worn on the head gear of the golfer and produces a positive feedback signal to the golfer upon proper execution of a golf swing. Such a device must be carefully adjusted to allow for the swing dynamics of each particular golfer, which complicates its use.
Another golf training device is taught in Johnson's U.S. Pat. No. 5,108,104, issued on Apr. 28, 1992. Such a device requires careful adjustment to each particular golfer's style, and assumes that a premature lifting of the golfer's head relative to striking the golf ball is physically differentiable from a properly timed lifting of the golfer's head relative to striking of the golf ball. Such a device relies solely upon a motion sensing means for input, and therefore is forced to provide feedback to the golfer based solely upon motion data. Motion data alone, however, is inadequate for determining correctness of an activity such as the lifting of one's head during or after a golf swing. The correctness of the lifting of the golfer's head is primarily determined not in how the head is lifted, but rather in the timing relative to the striking of the golf ball. Motion data alone does not pinpoint accurately when the golf ball was struck by the club in such cases.
U.S. Pat. No. 4,560,166 to Emerson on Dec. 24, 1985, teaches a golf training device worn on the head of the golfer that includes a motion sensor and a microphone for detecting the striking sound of the golf ball. Essentially, if the motion sensor detects that the golfer's head is in motion when the microphone detects the striking of the golf ball, a negative feedback alarm sounds. If the motion sensor detects that the golfer's head is stationary when the microphone detects the striking of the golf ball, the alarm is inhibited. Such a device overcomes the drawbacks of the "motion-only" prior art devices, but does have several critical drawbacks itself. Primarily, such a device takes the notification action of either sounding the alarm or not sounding the alarm immediately upon detection of trigger event, that is, the striking of the golf ball. Movement before or after the trigger event is ignored, which can be just as important in the correctness of the physical activity as the movement during the trigger event. For example, in shooting a rifle, a marksman can be trained to counter the kickback force of firing the rifle so as to keep the barrel of the rifle steady between shots. A training device of this type is useless because the sound of the gun firing occurs before the motion to be detected occurs.
Further, such a training device cannot discriminate between the sound of a correctly hit golf ball and the sound of an incorrectly hit golf ball. As such, while a golfer many not have lifted his head prematurely, he may have hit the golf ball incorrectly, causing an errant shot. For example, he may have hit the top hemisphere of the golf ball instead of hitting the golf ball at its horizontal equator. In such a case, the golfer will not receive the proper feedback concerning the correctness of his swing from such a training device.
There is a need for a physical activity training device which overcomes the disadvantages of known devices.